Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “HALIDES”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,747 records · Page 97
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Chemistry, Structure, and Function of Lone Pairs in Extended Solids

The lone pair has been a known feature of the electronic structure of molecules for over 100 years. Beginning with the pioneering work of Lewis and others that was later developed into useful guidelines for predicting molecular structure, lone pairs and their steric consequences are now taught at the very earliest stages of a chemistry education. In the crystalline solid state, lone pairs have perhaps had a less visible yet equally consequential role, with a significant impact on a range of properties and functionalities. Important properties associated with s 2 electron-derived lone pairs include their role in creating conditions favorable for ion transport, in the formation and correlation of local dipoles and the resulting polar behavior leading to ferroics and multiferroics, in increasing the refractive index of glass, in reducing the thermal conductivity of thermoelectric materials, and in breaking local symmetry permitting second-harmonic light generation.. In recent years, the role of the lone pair in developing the electronic structure of some topological quantum materials has also been recognized. While structural distortions due to lone pairs have traditionally been characterized through their crystallography, recent advances in scattering and spectroscopy have revealed the presence of local lone pair-driven distortions that do not correlate over long length scales. The role of these crystallographically “hidden” lone pairs, their detection, and their impact on properties have become a growing body of work in the literature. Hidden lone pairs are an effective argument for considering a role for lone pairs that goes beyond their being objects that occupy space in the coordination polyhedra of cations. This Account introduces the chemistry of lone pairs in extended crystalline solids, including a discussion of when they are stereochemically active, how they manifest in the structure, and how their chemistry can be tuned by the chemical environment around them. Eventually, all of these factors work in unison to help develop and tune properties of interest. Certain specific examples of structure–property relationships in materials that are driven by lone pair behavior are described here, including the potential impact of lone pairs on the optical and electronic properties of hybrid halide perovskite compounds that are relevant to their photovoltaic applications. Here, we highlight the role of lone pairs in the dielectric behavior of geometrically frustrated pyrochlores, the temperature-dependent optoelectronic behavior of halide perovskites, the polar phase transitions in lead-free ferroelectric perovskites, and the compositional insulator-to-metal transition in ruthenium pyrochlores. The theme underpinning this Account is that the lone pair can be considered to be a powerful design element for a broad range of material function.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Physical Properties of Candidate X-ray Detector Material Rb 4 Ag 2 BiBr 9

Recently, metal halide perovskites have emerged as promising semiconductor candidates for sensitive X-ray photon detection due to their suitable band gap energies, excellent charge transport properties, and low material cost afforded by their low-temperature solution-processing preparation. Furthermore, we report an improved methodology for single crystal growth and thermal and electrical properties of a two-dimensional (2D) layered halide material Rb 4 Ag 2 BiBr 9 , which has been identified as a potential candidate for X-ray radiation detection applications. The measured heat capacity for Rb 4 Ag 2 BiBr 9 implies that there are no structural phase transitions upon cooling. Temperature dependence of thermal transport measurements further suggests remarkably low thermal conductivities of Rb 4 Ag 2 BiBr 9 that are comparable to the lowest reported in literature. The bulk crystal resistivity is determined to be 2.59 × 10 9 Ω·cm from the current–voltage (I–V) curve. Density of trap states is estimated to be ~10 10 cm –3 using the space-charge-limited-current measurements. The fabricated Rb 4 Ag 2 BiBr 9 -based X-ray detector shows good operational stability with no apparent current drift, which may be ascribed to the 2D crystal structure of Rb 4 Ag 2 BiBr 9 . Finally, by varying the X-ray tube current to change the corresponding dose rate, the Rb4Ag2BiBr9 X-ray detector sensitivity is determined to be 222.03 μC Gy –1 cm –2 (at an electric field of E = 24 V/mm).

36 MATERIALS SCIENCE↗
DOE OSTI2020

0D and 2D: The Cases of Phenylethylammonium Tin Bromide Hybrids

Tin halide perovskites and perovskite-related materials have emerged as promising lead-free hybrid materials for various optoelectronic applications. While remarkable progress has been achieved in the development of organic tin halide hybrids with diverse structures and controlled dimensionalities at the molecular level, some controversial results that have been reported recently need to be addressed. For instance, different photophysical properties have been reported for two-dimensional (2D) (PEA) 2 SnBr 4 (PEA = phenylethylammonium) by several groups with distinct emission peaks at around 468 and 550 nm. Here we report our efforts in the synthesis of phenylethylammonium tin bromide hybrids with zero-dimensional (0D) and 2D structures, and characterizations of their structural and photophysical properties. 0D [(PEA) 4 SnBr 6 ][(PEA)Br] 2 [CCl 2 H 2 ] 2 was found to exhibit strong yellow emission peak at 566 nm with a photoluminescence quantum efficiency (PLQE) of ~90%, while 2D (PEA) 2 SnBr 4 had weak emission peak at 470 nm with a PLQE of <0.1%. Interestingly, 0D [(PEA) 4 SnBr 6 ][(PEA)Br] 2 [CCl 2 H 2 ] 2 can be converted into 2D (PEA) 2 SnBr 4 upon drying, which would return to 0D [(PEA) 4 SnBr 6 ][(PEA)Br] 2 [CCl 2 H 2 ] 2 upon addition of dichloromethane. Powder X-ray diffraction results confirmed the reversible transformation between 0D and 2D structures. Density functional theory calculations showed that excitons in 0D [(PEA) 4 SnBr 6 ][(PEA)Br] 2 [CCl 2 H 2 ] 2 are highly localized, resulting in a strongly Stokes shifted broadband emission, while delocalized electronic states in 2D (PEA) 2 SnBr 4 result in weaker exciton binding, a higher exciton mobility, and a higher nonradiative decay.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Ligand-Dependent Tuning of Interband and Intersubband Transitions of Colloidal CdSe Nanoplatelets

Although surface ligands of colloidal nanocrystals are known to adjust the absolute energy levels of valence and conduction bands of semiconductor nanocrystals, they typically have only minor influence on the band gap or effective masses. This changes in nanoplatelets. Ligand exchange of CdSe colloidal nanoplatelets induces large (up to 300 meV) bathochromic shifts of both interband and intersubband transitions. Here, three families of ligands-halides, thiolates, and phosphonates-are used to tune interband transitions, reflecting electron and hole confinement, across visible wavelengths and intersubband transitions, reflecting electron confinement, across the near-infrared spectral window. Furthermore, careful examination shows that delocalization from expansion of the nanoplatelet short axis, which was reported previously, cannot alone explain observed red shifts. Instead, comparison of intersubband, interband, and hole energy levels shows that ligand head group chemistry confers specific, idiosyncratic adjustments of the contribution of conduction and valence bands to the observed bathochromic shifts. Phosphonate ligands show the largest band gap reductions but the smallest red shift of intersubband transition energies; halide-exchanged samples displayed smaller reductions in band gap but large red shifts of intersubband transitions; thiolates fall in between. A related specificity is observed in hole states, which implicates ligand-responsive valence band curvature as an additional contribution driving optical changes. For nanoplatelets, surface ligand chemistry offers not only a tool to adjust the absolute energy level of conduction and valence bands but also an alternative route to preferential electron or hole band engineering that is normally achieved with inorganic shells.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Beyond Strain: Controlling the Surface Chemistry of CsPbI 3 Nanocrystal Films for Improved Stability against Ambient Reactive Oxygen Species

Colloidal halide perovskite nanocrystals (NCs) have the possibility of easy scale-up due to their batch synthesis and have demonstrated excellent optoelectronic properties. In particular, perovskite NCs have remarkably high photoluminescence quantum yields in solution and as thin films and impressive open circuit voltages in photovoltaic devices. Despite these promising results, little work has been done to understand the stability of CsPbI 3 NCs for optoelectronic device applications. It has been previously shown that the ligands impart tensile surface strain, which stabilizes the black three-dimensional (3D) perovskite phase against phase degradation, making CsPbI 3 NCs some of the most structurally robust inorganic halide perovskites to date. However, understanding exactly how CsPbI 3 NCs degrade under ambient conditions is critical. Additionally, we demonstrate that the degradation mechanism of NCs is unique from, and 2 orders of magnitude slower than, their polycrystalline thin-film counterparts. Under specific conditions, CsPbI 3 NC films show a compositional instability instead of the phase instability seen in large grain CsPbI 3 . This is mediated through reactions with superoxide and other reactive oxygen species, which are initiated from surface defect states, O 2 and light. We then use this mechanistic insight to identify multiple strategies to prolong the lifetimes of CsPbI 3 NC films, by going beyond surface strain to mitigate key surface chemistries. We demonstrate that (1) minimizing the number of surface defects (2) using an alkylammonium bromide ligand surface treatment and (3) encapsulation with an oxygen scavenging layer all increase NC film lifetimes by inhibiting various steps in the photo-oxidation degradation reaction.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Solvent and A-Site Cation Control Preferred Crystallographic Orientation in Bromine-Based Perovskite Thin Films

Preferred crystallographic orientation in polycrystalline films is desirable for efficient charge carrier transport in metal halide perovskites and semiconductors. However, the mechanisms that determine the preferred orientation of halide perovskites are still not well understood. In this work, we investigate crystallographic orientation in lead bromide perovskites. We show that the solvent of the precursor solution and organic A-site cation strongly affect the preferred orientation of the deposited perovskite thin films. Specifically, we show that the solvent, dimethylsulfoxide, influences the early stages of crystallization and induces preferred orientation in the deposited films by preventing colloidal particle interactions. Additionally, the methylammonium A-site cation induces a higher degree of preferred orientation than the formamidinium counterpart. We use density functional theory to show that the lower surface energy of the (100) plane facets in methylammonium-based perovskites, compared to the (110) planes, is the reason for the higher degree of preferred orientation. In contrast, the surface energy of the (100) and (110) facets is similar for formamidinium-based perovskites, leading to lower degree of preferred orientation. Furthermore, we show that different A-site cations do not significantly affect ion diffusion in bromine-based perovskite solar cells but impact ion density and accumulation, leading to increased hysteresis. Our work highlights the interplay between the solvent and organic A-site cation which determine crystallographic orientation and plays a critical role in the electronic properties and ionic migration of solar cells.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Orientational Order in Spin-Cast Lead-Iodide Perovskite Nanocrystal Solids

Combined synthetic control over size and composition renders colloidal lead-halide perovskite nanocrystals a tunable platform for high-efficiency optoelectronic applications. However, the properties and operational stability of devices based on nanocrystal solids are often dictated by the method of the evaporation-induced assembly. Ubiquitous slow evaporation techniques can produce highly ordered nanocrystal domains but limit the prospects for scalable fabrication of continuous device layers, calling for investigation of approaches to more rapidly form ordered perovskite nanocrystal solids. Here, we study orientationally ordered lead-iodide perovskite nanocrystal solids prepared by conventional spin coating with molecular additives (excess ligand) to enhance ordering within the arrays. In situ X-ray scattering measurements reveal that orientational ordering occurs rapidly upon solvent removal during spin coating and can be further enhanced by manipulating the spin speed. We vary the additive ligand length and explore trade-offs between ordering and layered perovskite impurity formation. Arrays treated with the intermediate-length octylamine ligand exhibit increased in-plane electronic conductivity, suggesting orientational ordering and internanocrystal electronic coupling can be enhanced by the treatment. In conclusion, these results highlight the prospects of establishing long-range order in lead-halide perovskite nanocrystal solids by using simple and fast coating methods.

14 SOLAR ENERGY↗
DOE OSTI2024

Smaller Is Better: The Case for Lower-Order Iodoplumbate Species Dominating MAPbI 3 /Dimethylformamide Solutions

Here, using complementary experimental measurements and computational predictions of spectroscopic measurements (EXAFS, XANES, and UV–vis), we have determined the identity of the most stable iodoplumbate species in dilute lead halide perovskite precursor solutions. We have determined which species are most likely to be thermodynamically stable compared to others that are unstable or metastable. Condensed phase ab initio models were constructed, and the resulting ensembles were used to directly compare the computed signals to the experimental results of the EXAFS, XANES, and UV–vis spectra of PbI 2 :MAI in DMF. The results of this study suggest that only Pb 2+ , PbI + , and PbI 2 are dominant in the dilute lead perovskite precursor solutions as thermodynamically stable entities. Our interpretation of the relative stability of iodoplumbate species in solution, based on an analysis of EXAFS and XANES spectra, provides critically important new insight into the species most likely to be responsible for crystal nucleation and growth in these materials. This insight will have a significant consequence on the broad scientific community and will necessitate the reinterpretation of peaks in the UV–vis spectra of lead halide perovskite precursor solutions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Crystal and Electronic Structures of Complex Bismuth Iodides A 3 Bi 2 I 9 ( A = K, Rb, Cs) Related to Perovskite: Aiding the Rational Design of Photovoltaics

Ternary bismuth halides form an interesting functional materials class in the context of the closely related Pb halide perovskite photovoltaics, especially given the significantly reduced toxicity of Bi when compared with Pb. The compounds A 3 Bi 2 I 9 (A = K, Rb, Cs) examined here crystallize in two different structure types: the layered defect-perovskite K 3 Bi 2 I 9 type, and the Cs 3 Cr 2 Cl 9 type. The latter structure type features isolated Bi 2 I 9 3– anions. Here, the crystal structures of the ternary iodides are redetermined and a corrected structural model for Rb 3 Bi 2 I 9 , as established by single crystal X-ray diffraction and solid state 87Rb NMR spectroscopy and supported by density functional theory (DFT) calculations is presented. A variety of facile preparation techniques for single crystals, bulk materials, as well as solution-processed thin films are described. The optical properties and electronic structures are investigated experimentally by optical absorption and ultraviolet photoemission spectroscopy and computationally by DFT calculations. Absolute band positions of the valence and conduction bands of these semiconductors, with excellent agreement of experimental and calculated values, are reported, constituting a useful input for the rational interface design of efficient electronic and optoelectronic devices. The different structural connectivity in the two different structure types, somewhat surprisingly, appears to not impact band positions or band gaps in a significant manner. Computed dielectric properties, including the finding of anomalously large Born effective charge tensors on Bi 3+ , suggest proximal structural instabilities arising from the Bi 3+ 6s 2 lone pair. These anomalous Born effective charges are promising for defect screening and effective charge carrier transport. The structural, electronic, and optical properties of the complex bismuth iodides are to some extent similar to the related lead iodide perovskites. In conclusion, the deeper valence band positions in the complex bismuth iodides point to the need for different choices of hole transport materials for Bi-iodide based solar cell architectures.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Dissecting Disorder: Defect-Driven Structural Complexity in Layered Li3InCl6 Solid Electrolyte

Halide solid electrolytes have emerged as promising candidates for solid-state batteries owing to their high oxidative stability and ionic conductivity. Among them, Li3InCl6 (LIC) has attracted significant attention. However, diffraction patterns of LIC synthesized via different methods exhibit distinct differences particularly at low-angle reflectionsindicative of underlying structural disorder. These variations are attributed to deviations from ideal crystallographic order, especially stacking faults, whose impact on structure and ion transport remains poorly understood. Here, we identify and quantify stacking faults in LIC samples prepared under different synthetic conditions. Using X-ray diffraction and time-of-flight neutron diffraction, we construct and refine stacking fault models that accurately reproduce the experimental diffraction features. LIC samples with higher degrees of stacking faults exhibit only negligible differences in ionic conductivities and activation energies. This indicates that stacking faults have a limited impact on altering the Li+ diffusion pathway along the c-axis, likely due to the high concentration of vacancies in the In layers, while Li+ diffusion remains nearly unchanged in the ab-plane. Our results account for the observed differences in diffraction patterns across samples and provide a quantitative assessment of faulting probabilities and stacking sequences. The insights gained from this study are expected to be broadly applicable to other layered halide solid electrolytes and contribute to a deeper understanding of the role of structural disorder in ion transport.

Liu, Jue [ORNL] (ORCID:000000024453910X)↗
DOE OSTI2025

Polymorphism and Phase Control in Dion–Jacobson 2D 3-(Aminomethyl)piperidinium-Based Metal Iodide Perovskites

Two-dimensional halide perovskites exhibit rich structural diversity and tunable optoelectronic properties, making them promising materials for energy, sensing, and photonic applications. In this work, we report the structural mapping of four distinct polymorphs, γ (P2 1 /c), β (P4/mbm), α (P4/mmm), and δ (Cmcm) in the two-dimensional iodoplumbate, iodostannate, and iodogermanate perovskite so-called Dion-Jacobson series (3AMP)MI4 (M = Sn, Pb, Ge), where 3AMP is 3-(aminomethyl)piperidinium. The phases exhibit systematic evolution in octahedral distortion, lattice symmetry, and metal–halide geometry, enabling structural control over optoelectronic properties. Notably, the α-phase of (3AMP)SnI 4 represents a rare, ambient-stable, high-symmetry structure for Sn-based perovskites, without a phase transition down to 100 K. Variable-temperature single-crystal diffraction, powder x-ray diffraction (PXRD), and calorimetry reveal metal- and temperature-dependent polymorph interconversions, including the emergence of long range supercell reflections in Pb-rich compositions at low temperature. Optical spectroscopy and photoelectron yield spectroscopy confirm band gap tunability and band alignment trends, highlighting symmetry-dependent shifts and anomalous band gap bowing in mixed-metal systems, verified by electronic structure calculations. Calculations additionally indicate that the higher symmetry phases have reduced electron and hole effective masses compared to the lower symmetry phases.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Shifting Defect Self-Regulation via Disordered Vacancies in Hollow Tin Perovskites

Tin(II)-based hybrid halide perovskites typically suffer from severe self-doping behavior as a result of facile oxidation of Sn(II) to Sn(IV), leading to high carrier densities (holes) and metallic-like conductivities that limit their applications. In this contribution, we describe how substituting the large ethylenediammonium cation for methylammonium in the intentionally defective “hollow” perovskite family, MA 1−x en x Sn 1−0.7x I 3−0.4x (MA = methylammonium, en = ethylenediammonium), where 0 ≤ x ≤ 0.38, effectively minimizes the intrinsic self-doping behavior. The use of a solvent-free, mechanochemical synthesis route further circumvents oxidative side reactions typical in solution processing, enabling more precise control and understanding of both composition and defect chemistry. Dark and time-resolved microwave conductivity measurements of these materials as a function of “x” reveal two regimes of conductivity suppression: at low x incorporation (x ≤ 0.15), the carrier density decreases by an order of magnitude via defect-mediated charge compensation, while higher substitution (0.15 < x ≤ 0.38) greatly reduces the carrier mobility. At these lower substitution levels, the observations suggest that intrinsic equilibrium tin vacancies are compensated instead by ionic defects in lieu of mobile holes. For the higher substitution levels, the less mobile carriers exhibit long recombination lifetimes, consistent with polaron-mediated transport. These findings establish a strategy for relatively low iodine chemical potential synthesis and defect-driven control of the carrier concentration in tin halide perovskites, advancing the rational discovery of dopable hybrid semiconductors.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Searching for “Defect-Tolerant” Photovoltaic Materials: Combined Theoretical and Experimental Screening

Recently, we and others have proposed screening criteria for 'defect-tolerant' photovoltaic (PV) absorbers, identifying several classes of semiconducting compounds with electronic structures similar to those of hybrid lead-halide perovskites. In this work, we reflect on the accuracy and prospects of these new design criteria through a combined experimental and theoretical approach. We construct a model to extract photoluminescence lifetimes of six of these candidate PV absorbers, including four (InI, SbSI, SbSeI, and BiOI) for which time-resolved photoluminescence has not been previously reported. The lifetimes of all six candidate materials exceed 1 ns, a threshold for promising early stage PV device performance. However, there are variations between these materials, and none achieve lifetimes as high as those of the hybrid lead-halide perovskites, suggesting that the heuristics for defect-tolerant semiconductors are incomplete. Here, we explore this through first-principles point defect calculations and Shockley-Read-Hall recombination models to describe the variation between the measured materials. In light of these insights, we discuss the evolution of screening criteria for defect tolerance and high-performance PV materials.

14 SOLAR ENERGY↗
DOE OSTI2018

Photovoltaic Effect in Indium(I) Iodide Thin Films

Currently, halide semiconductors are undergoing a period of intense interest, buoyed by the outstanding optoelectronic properties of hybrid perovskites. It is worthwhile to consider whether related materials sharing unique aspects of the perovskite chemistry, such as the incorporation of metals that provide lone pair $s$ electrons when integrated within the halide lattice, might yield semiconductors with comparable properties. One such metal that has not been widely studied in the context of photovoltaics is monovalent indium. In this work, we investigate a method of depositing films of indium(I) iodide, coupled with optoelectronic characterization and incorporation of these films into thin-film solar cells. We find that, although indium(I) iodide exhibits a photovoltaic effect, it is likely to be compromised by difficult-to-remove defects, e.g., iodine vacancies, which are expected to introduce recombination centers deep within the band gap.

36 MATERIALS SCIENCE↗
DOE OSTI2019

GeI 2 Additive for High Optoelectronic Quality CsPbI 3 Quantum Dots and Their Application in Photovoltaic Devices

Trioctylphosphine (TOP)-based syntheses of CsPbI 3 perovskite quantum dots (QDs) yield unprecedented high photoluminescence quantum yield (PL QY), lower Stokes shifts, and longer carrier lifetimes due to their enhanced crystallinity. This synthetic route relies on a heavily Pb-rich condition or a large Pb:Cs molar ratio in precursor solution to produce QDs with appropriate stoichiometry as well as to guarantee a good colloidal stability. The high Pb condition is achieved by a high concentration of PbI 2 prepared in TOP. Here we find such Pb-rich strategies can be avoided by providing additional iodine ions using other metal halide salts. In particular GeI 2 , which contrary to PbI 2 , readily dissolves in TOP. CsPbI 3 QDs prepared using PbI 2 /GeI 2 combination show near-unity PL QY and improved chemical stability compared to the previous synthetic route. Furthermore, we find no sign of Ge incorporation in the QDs (compositionally or energetically). The ensuing QD solar cells deliver power conversion efficiency of 12.15% and retain 85% of its peak performance after storage over 90 days. The PbI 2 /GeI 2 dual-source iodine synthetic approach presented here represents a more rational and robust route to high-quality CsPbI 3 QDs. to guarantee a good colloidal stability. The high Pb condition is achieved by a high concentration of PbI2 prepared in TOP. Here we find such Pb-rich strategies can be avoided by providing additional iodine ions using other metal halide salts. In particular GeI 2 , which contrary to PbI 2 , readily dissolves in TOP. CsPbI 3 QDs prepared using PbI 2 /GeI 2 combination show near-unity PL QY and improved chemical stability compared to the previous synthetic route. Furthermore, we find no sign of Ge incorporation in the QDs (compositionally or energetically). The ensuing QD solar cells deliver power conversion efficiency of 12.15% and retain 85% of its peak performance after storage over 90 days. The PbI 2 /GeI 2 dual-source iodine synthetic approach presented here represents a more rational and robust route to high-quality CsPbI 3 QDs.

14 SOLAR ENERGY↗
DOE OSTI2019

Probing the Stability and Band Gaps of Cs 2 AgInCl 6 and Cs 2 AgSbCl 6 Lead-Free Double Perovskite Nanocrystals

Lead toxicity has sparked interest into alternative halide nanomaterials with properties similar to CsPbX 3 perovskites. A promising alternative predicted from bulk studies is the family of double perovskites of the form Cs 2 AgMX 6 . In this work, we report the synthesis of colloidal CsCs 2 AgInCl 6 and Cs 2 AgSbCl 6 nanocrystals via injection of acyl halides into a metal acetate solution under atmospheric conditions and relatively mild temperatures. We reflect the synthesis of single-crystalline cubic nanocrystals of ca. 10 nm side length and their morphological similarities to other double perovskite nanostructures in terms of their [200] facet termination and decoration with Ag (o) smaller nanocrystallites. To contrast the stabilities of the synthesized materials, we develop a titration assay based on the degradation of nanocrystals with amines as a proxy for degradation by humidity, which provides a quantifiable stability metric. This measurement shows that Cs 2 AgSbCl 6 releases more than twice the decomposition energy compared to Cs 2 AgInCl 6 or CsPbCl 3 and degrades in the presence of approximately one molar equivalent of amine, whereas the other two materials require more than a 100-fold excess. Using facile chemical titration to quantitatively determine chemical stability provides an additional tool to aid in the basic understanding of what makes some of these materials more environmentally stable than others.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗